The present invention relates to a method for making flexible circuits.
At present, flexible circuits are mainly made by depositing a conductive pattern on a film of a polymeric material such as polyester, and polyimide, followed by a chemical removal process for removing parts not pertaining to the circuit being made.
Flexible circuits may also be made by suitably metallized textile substrates.
Is also herein mentioned the well known etching process in which the material is mainly removed by chemical radical reactions with the substrate.
The etching chemical process is performed for creating preset patterns on a metallized fabric material.
A first stage of a chemical etching process is to prepare functional masks for forming on the metallized fabric a desired pattern.
By a photolithographic or photo-etching process, the thus made pattern is transferred from its mask to a thin layer of a UV radiation sensible material covering the surface of a textile substrate.
In order to generate the target flexible electronic elements, an etching or chemical process is performed for selectively removing unmasked portions of the fabric material covering metal layer.
The photolithographic steps are as follows:                applying the photosensible film (resist) on the substrate;        exposing to a UV radiation the resist film at regions thereof not covered by the pattern defined on a photolithographic mask contacting the substrate;        developing the resist film at the exposed regions thereof (the so called positive process);        etching the metal film underlining the photo sensitive film at the regions not covered thereby;        stripping.        
The developing is the operating step which mostly affects the pattern quality.
The etching is the process used for tracing elements, consisting of eliminating excess metal while leaving only the designed circuit connections.
The removal is carried out by an acid bath.
Etching reagent, etching time and related temperature and stirring are the main factors controlling this process.
The stripping is the process carried out for removing a still present photosensible film.
It is important that the stripping procedure does not negatively affect the underlying metal layer and does not cause contamination thereof.